Search Results (656)

A 2D multiphase-flow coupling simulation model for preparing nanocrystalline ribbons using planar-flow casting (PFC) with a cooling roller was established. The influence of roller speed on molten pool characteristics, cooling-roller heat transfer, and ribbon thickness was analyzed. The effect of ribbon thickness on the total loss and permeability of the magnetic cores was investigated. The results indicate that the molten pool size decreased as the roller speed increased. At t = 5 ms, the maximum heat-transfer coefficient of the roller surface increased from 2.09 × 10⁶ W·m⁻²·K⁻¹ at 15 m/s to 2.6 × 10⁶ W·m⁻²·K⁻¹ at 24 m/s. The ribbon thickness decreased from 39.96 μm to 20.02 μm (a 49.9% reduction) as the roller speed increased from 18 m/s to 30 m/s. The total loss of the nanocrystalline magnetic cores increased with ribbon thickness, whereas their permeability increased as ribbon thickness decreased. At 100 kHz, the nanocrystalline magnetic core made of 10–12 μm ribbons exhibited a high permeability of 59,507. Full article

Nitridation of different materials using ion implantation is of considerable interest for many applications. As electronic components, oxynitride (SiO_xN_y) layers exhibit beneficial properties such as precise compositional variability, refractive index tunability, oxidation resistance, and low mechanical stress. In the present study we investigate nanoscale SiO_xN_y synthesized using ion implantation methods. To introduce N⁺ ions into a shallow Si subsurface region, both conventional ion beam implantation and plasma immersion ion implantation with subsequent high-temperature treatment in dry O₂ are used. The optical and morphological properties and chemical bonding of formed SiO_xN_y layers were studied by applying spectroscopic ellipsometry in the range of VIS-Near IR (SE) and IR (IR-SE), Raman spectroscopy and Atomic Force Microscopy (AFM). Monte Carlo modeling of implant profiles contributed to understanding physical and chemical processes and predicted different influences of the incorporated N⁺ ions on the oxidation mechanism, confirmed by the thickness dependence of SiO_xN_y/Si layers obtained from the SE data analysis. IR-SE spectral analysis established the formation of Si-O, Si-N, Si-N-O and Si-Si chemical bonds in the grown layers. The occurrence of amorphization of the Si crystal lattice due to incorporation of high-energy N⁺ ions into the Si lattice is confirmed by the Raman and ellipsometry results. The free Si atoms can congregate, forming nanocrystalline clusters. AFM imaging revealed that both implantation methods left the surface of the resulting SiO_xN_y layers considerably smooth with similar roughness parameter values. The results of the studies imply that the technological approaches used allow the production of high-quality nanoscale silicon oxynitride films with appropriate tunable composition and properties for possible application in advanced electronic devices for nanoelectronics, optoelectronics and sensor applications. Full article

Hybrid nanomaterials integrating magnetic and semiconductor phases offer promising multifunctional platforms for wastewater remediation; however, their stabilization and recovery remain challenging. In this study, Fe₃O₄ and ZnTiO₃/TiO₂ nanoparticles were incorporated into a rice husk ash-based geopolymer matrix to develop hybrid nanocomposites for synergistic adsorption–photodegradation of methylene blue (MB) and methyl orange (MO). The materials were synthesized via alkaline activation followed by nanoparticle incorporation, and characterized by XRD, XRF, FTIR, SEM, EDX, BET surface area analysis, and pHPZC determination. XRD confirmed the presence of nanocrystalline Fe₃O₄ and ZnTiO₃/TiO₂ phases while preserving the amorphous aluminosilicate framework. Modified powders exhibited higher specific surface areas (up to 198 m² g⁻¹) compared to the unmodified geopolymer. Adsorption followed the Langmuir isotherm and pseudo-second-order kinetics, with spontaneous and exothermic behavior. Under UV irradiation, the ZnTiO₃/TiO₂-modified composite achieved photodegradation efficiencies up to 94% for MB and 92% for MO, whereas the Fe₃O₄-modified material combined adsorption capacity with magnetic recoverability. These results demonstrate that nanoparticle incorporation enables multifunctional performance while maintaining structural integrity of the geopolymeric matrix. Full article

Nanostructured metallic materials are widely applied in various fields due to their excellent comprehensive properties. Enhancing mechanical properties through microstructure design has emerged as a novel strengthening strategy. In this contribution, the microscopic mechanical behavior of coarse-grained and gradient-structured nanocrystalline NiCoAl alloys during tensile deformation was investigated via molecular dynamics simulations. Based on the investigation of compositional effects, the Ni₆₀Co₃₀Al₁₀ alloy composition was selected, exhibiting a yield strength of 4.92 GPa. The results indicate that increasing Al content reduces the material’s strength, Young’s modulus, and work hardening effect. Furthermore, by introducing a gradient structure with grain sizes gradually varying from 1.8 nm to 6.5 nm into the alloy, the yield strength reaches 1.8 GPa and the flow stress reaches 3.35 GPa, demonstrating a significant improvement compared to the uniform coarse-grained structure. Upon introducing the gradient structure into the alloy, it was observed that geometrically necessary dislocations (GNDs) nucleate in the coarse-grained region during deformation and gradually extend towards the fine-grained region. The increased grain boundary density effectively impedes dislocation motion and enhances dislocation pinning capability, thereby inducing continuous strain hardening and improving plasticity. By promoting the accumulation and interaction of grain boundary dislocations, the gradient structure achieves further strengthening and strain hardening in the alloy, providing a theoretical basis and simulation foundation for designing high-performance advanced alloys. Full article

To meet the power supply requirements of autonomous underwater vehicles (AUVs) in dynamic ocean environments, this study proposes a wireless power transfer (WPT) system for AUVs, incorporating novel nanocrystalline flake ribbon cores. The proposed system utilizes the excellent magnetic field concentrating and shielding characteristics of nanocrystalline materials. The flake ribbons are fabricated by compressing dielectric materials mixed with nanocrystalline ribbons, which effectively reduces eddy-current loss. The layout arrangement of nanocrystalline materials is investigated, and a magnetic coupler employing ribbon-type nanocrystalline materials is adopted based on simulation analysis and comparison. The influence of nanocrystalline materials on the mutual inductance distribution between the transmitting and receiving coils is explored. Considering the potential positional misalignments between the transmitting and receiving coils in practical marine environments, the misalignment tolerance of the system is comprehensively analyzed and experimentally verified. An experimental prototype is established, and the results demonstrate that the proposed magnetic coupler design significantly improves the performance of the WPT system. Compared with the conventional WPT system without nanocrystalline flake ribbon cores, the proposed design effectively increases the power transfer efficiency by 2.99% and greatly stabilizes the output power by 36%. This study validates the effectiveness and practicability of using nanocrystalline flake ribbon cores in WPT systems for AUV applications. Full article

Diamond coatings with three distinct surface textures, namely spherical, pyramidal, and prismatic morphologies, were fabricated using the hot-filament chemical-vapor deposition (HFCVD) method. Scanning electron microscopy (SEM) was employed to analyze the surface morphological characteristics and differences among the coatings. Raman spectroscopic analysis further confirmed that all three diamond films exhibited excellent deposition uniformity and high crystalline quality. A three-dimensional optical microscopy system was used to measure the surface roughness values, which were determined to be Ra 0.423 μm, Ra 0.515 μm, and Ra 0.809 μm, respectively. An HFCVD diamond-coated tool was innovatively employed for the lapping of sapphire wafers, enabling a systematic investigation of the tribological behavior during the lapping process. Based on the experimental results, three morphological material removal models were established. The study demonstrates that the spherical diamond coating achieves a superior surface finish (Ra 0.22 μm) due to its continuous multi-point contact geometry, governed by the agglomerated nanocrystalline structure. Sample 3 had the highest removal rate of 24.3 μm/min. This is related to its surface morphology characteristics and is also due to the two-body contact between the diamond-coated tool and sapphire, offering a high-efficiency alternative for precision machining. Full article

Starch–polyphenol interactions play a critical role in regulating the structural organization and thermal behavior of starch-based systems. In this study, maize starches with different amylose contents were used to systematically investigate how tea polyphenol (TP) complexation influences starch structure and thermal stability. Starch–TP complexes were prepared under thermal-induced conditions and characterized using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). TGA results showed that increasing amylose content slightly reduced the thermal stability of native starches, whereas TP incorporation significantly enhanced thermal resistance, particularly in high-amylose systems. XRD analysis indicated that TP complexation did not affect the crystal structure of starch but led to a pronounced reduction in relative crystallinity, with low-amylose complexes exhibiting predominantly amorphous behavior and high-amylose complexes retaining partial nanocrystalline organization. FTIR spectra revealed reduced short-range molecular order and strengthened hydrogen bonding interactions after TP binding. DSC analysis demonstrated increased gelatinization temperatures accompanied by decreased enthalpy changes, reflecting restricted molecular mobility and delayed solvation of nanocrystalline domains. SEM observations further showed a transition toward denser and more interconnected micro–nano structures with increasing amylose content. Overall, TP preferentially interacts with amylose-rich regions through non-covalent interactions, promoting structural reorganization and enhanced thermal stability of the starch matrix. These findings provide new insight into amylose-dependent starch–polyphenol interactions and offer guidance for designing thermally stable starch-based functional materials. Full article

This paper presents a comprehensive experimental study addressing the lack of consistent low-temperature data on magnetic materials for high-efficiency cryogenic power electronics. A unified dataset is provided for the first time, covering temperatures from room temperature down to −194 °C, excitation frequencies between 25 kHz and 400 kHz, and technologically relevant flux densities. The investigated materials include MnZn- and NiZn-ferrites, nanocrystalline alloys (Vitroperm, Finemet), and various classes of alloyed powder cores. The characterization comprises magnetic hysteresis behavior, saturation flux density, temperature- and frequency-dependent core losses, permeability, and DC bias performance under cryogenic conditions. The results demonstrate that nanocrystalline materials and selected powder cores (MPP, Edge) exhibit superior cryogenic performance, while ferrites and low-cost powder cores suffer from significant loss increases or magnetic instability at low temperatures. These findings provide a solid basis for the selection and design of magnetic components in next-generation cryogenic power-electronic systems. Full article

This study presents an integrated low-temperature processing route that converts tungstic acid and ammonium paratungstate derived from scheelite ore (CaWO₄) into nanoscale tungsten trioxide (WO₃), metallic tungsten (W), and tungsten carbide (WC) via solid-state reaction, hydrogen reduction, and gas–solid reaction, respectively. This approach enables particle size control, reduced energy consumption, and enhanced functional properties, enabling evaluation of the materials’ performance in the oxygen evolution reaction (OER). X-ray diffraction (XRD) confirmed the formation of the desired phases with nanocrystalline structures and average crystallite sizes of 13.3 nm (WO₃), 31.55 nm (W), and 10.35 nm (WC). The materials exhibited homogeneous morphologies, demonstrating the effectiveness of the synthesis routes. Electrochemical measurements revealed promising OER activity; the WO₃ electrode showed the lowest overpotential of 321 mV at 10 mA cm⁻², while W and WC showed 327 mV and 340 mV, respectively, in 1.0 M KOH. Overall, the results demonstrate a strategy for scheelite valorization. Full article

This paper analyses a method for measuring the magnetization curves of ferrite and nanocrystalline materials and determining the loss of the ferromagnetic material used in inductor and transformer cores. Analogue and digital methods for determining B(H) characteristics and the corresponding measurement setup are described. Limitations of the analogue method are highlighted, and example magnetization characteristics obtained using both methods over a wide range of flux density amplitude and frequency changes are shown and discussed. Using the magnetization curves measured using both methods, the dependence of the loss of the tested cores on the frequency and amplitude of flux density was determined. It was demonstrated that the classical analogue hysteresis method produces distorted B(H) waveforms and significantly overestimated values of loss for the tested materials compared to the manufacturer’s data. An analysis was also conducted of the suitability of the classical Steinmetz model for modelling the dependence of the loss of the considered materials on the frequency and amplitude of magnetic flux density. It was demonstrated that the coefficients in this formula should be dependent on the above-mentioned quantities to achieve satisfactory accuracy between the model and the manufacturer’s data. Using a digital method for measuring the hysteresis loop of a ferromagnetic core and measuring its temperature using an optical method, the thermal resistance values of the tested cores were determined. Using the digital measurement method and the modified Steinmetz formula, a significant improvement in the accuracy of determining the losses of ferrite and nanocrystalline cores was achieved. Full article

This study aims to enhance the corrosion property of 17-4PH martensitic stainless steel, a material commonly used in industrial applications including nuclear power components, to enhance its performance in borate buffer solutions. The study employed plasma-based low-energy nitrogen ion implantation at temperatures ranging from 350 °C to 550 °C for 4 h to modify the steel surface. Microstructural characterization via XRD and TEM revealed the formation of a nanocrystalline nitrided layer, with thickness increasing from 11 to 27 μm and surface nitrogen concentration rising from 29.7 to 33.1% as temperature increased. Correspondingly, the nanocrystalline grains coarsened from an average size of 2 nm to 15 nm. The main findings showed that all nitrided layers significantly improved general corrosion resistance in pH 8.4 borate solution compared to the unmodified steel. An optimal performance with a corrosion potential of −169.4 mV(SCE) and a passive current density of 0.5 μA/cm² was achieved at 450 °C, accompanying the development of a denser passive film with high polarization resistance and lower defect density. It is concluded that the high interstitial nitrogen concentration within the nanocrystalline γ′_N accelerates passivation kinetics and enhances corrosion resistance, with the applied point defect model clarifying the underlying improvement mechanism. Full article

To address the clinical urgency of simultaneously monitoring multiple biomarkers in chronic wound infections, this study presents the innovative development of an electrochemical sensor based on a MWCNTs/MXene/PVA composite hydrogel. A dual-channel conductive network is constructed via the electrostatic self-assembly of the two-dimensional material MXene and multi-walled carbon nanotubes (MWCNTs). This strategy not only enhances the charge transfer efficiency but also effectively suppresses the aggregation of MWCNTs and exposes the electrocatalytic active sites. Additionally, the thermal annealing process is incorporated to facilitate the ordered arrangement of polyvinyl alcohol (PVA) nanocrystalline domains, strengthening the hydrogen bond-mediated interfacial adhesion and resolving the issues of hydrogel swelling and delamination. The detection limit (LOD) of the optimized sensor (MWCNTs_0.6/MXene_0.4/PVA) for pyocyanin (PCN) within complex biological matrices, including phosphate-buffered saline (PBS), Luria–Bertani (LB) broth, and saliva, was decreased to a range of 0.84~0.98 μM. Leveraging the disparities in the characteristic oxidation potentials (ΔE > 0.3 V) of PCN, uric acid (UA), and histamine (HA) in simulated wound exudate (SWE), the multi-component synchronous detection functionality of the non-specific sensor was expanded for the first time. This study offers a high-precision and multi-parameter integrated approach for point-of-care testing (POCT) of wound infections. Full article

Aiming at the key problems of the material removal rate and surface integrity of existing tools in the lapping of sapphire hard and brittle crystals, an efficient lapping tool has been developed to explore a new process for HFVCD (hot filament chemical vapor deposition) diamond tools to efficiently lap sapphire wafers. With the premise of ensuring the surface roughness of the wafer is Ra ≤ 0.5 μm, the material removal rate is increased to more than 1 μm/h. To explore a high-efficiency lapping process for sapphire wafers using HFCVD diamond tools. The influence of key preparation parameters on the surface characteristics of CVD (chemical vapor deposition) diamond films was systematically investigated. Three types of CVD diamond coating tools with distinct surface morphologies were fabricated. These tools were subsequently employed to conduct lapping experiments on sapphire wafers in order to evaluate their processing performance. The experimental results demonstrate that the gas pressure, methane concentration, and substrate temperature collectively influenced the surface morphology of the diamond coatings. The fabricated coatings exhibited well-defined grain boundaries and displayed pyramidal, prismatic and spherical features, corresponding to high-quality microcrystalline and nanocrystalline diamond layers. In the lapping experiments, the prismatic CVD diamond coating tool exhibited the highest material removal rate, reaching approximately 1.7 μm/min once stabilized. The spherical diamond coating tool produced the lowest surface roughness on the lapped sapphire wafers, with a value of about 0.35 μm. Surface morphology-controllable diamond tools were used for the lapping processing of the sapphire wafers. This achieved a good surface quality and high removal rate and provided new ideas for the precision machining of brittle hard materials in the plane or even in the curved surface. Full article

Nanocrystalline Fe-Gd-B alloys were successfully synthesized via Gd alloying in a binary Fe-B system using a single-roller melt-spinning technique. A systematic investigation of Gd content variation (0–4.35 at.%) reveals its critical role in tuning microstructure evolution, thermal stability, and magnetic properties. Crucially, the Fe_90.70Gd_2.32B_6.98 alloy ribbon exhibits optimized magnetic performance, achieving a high saturation magnetic induction (B_s) of 1.67 T and a low coercivity (H_c) of 2.737 kA/m. This enhancement is attributed to the suppression α-Fe grain growth through Gd-induced elevation of the thermal stability of the amorphous matrix, which confines the average crystallite size to 26.3 nm. The refined α-Fe phase contributes to elevated B_s through an increased ferromagnetic fraction, while its nanoscale grain structure, combined with wide magnetic domain configurations, effectively reduces H_c by limiting domain wall pinning sites. These findings establish that the synergistic effect of Gd alloying and Fe/B ratio adjustment is a viable strategy for designing high-performance Fe-based magnetic alloys. Full article

Double complex salts (DCSs) of the composition [Co(NH₃)₆][Fe(CN)₆] are a promising precursor for the preparation of catalysts for the hydrogenation of carbon oxides (CO and CO₂) by Fischer–Tropsch synthesis. The specific surface area is an important parameter for catalysts. Our article investigates the influence of mechanochemical activation (MCA) on this DCS in order to determine the conditions for obtaining the largest specific surface area of the intermetallic compound, a product of the DCS thermolysis. In this work, the effect of MCA on the physicochemical properties of the DCS [Co(NH₃)₆][Fe(CN)₆] and the products of its thermal decomposition in an argon atmosphere were investigated. It was shown that MCA leads to partial reduction of Fe⁺³ to Fe⁺², changes in the coordination of ammonia, amorphization of the structure and a decrease in the thermal stability of DCS. Thermolysis at 650 °C of samples subjected to MCA for 10 min results in the formation of nanocrystalline intermetallic compound Co_0.5Fe_0.5. The results demonstrate the potential of using MCA to control the properties of functional materials based on DCS. Full article